As the processing power available to devices and associated support services continues to increase, it has become practical to interact with users in new ways. In particular, it has become practical to interact with users through two-way speech dialogs, in a which user instructs a system by voice and the system responds by speech.
Although it is possible in many environments to reliably recognize and understand user speech, certain environments, particularly environments containing higher levels of non-voice interference, may make speech recognition and understanding difficult.